For having an effective heat exchange, the prior art has tought heat exchangers comprising a vat having an open side on which is fastened a header tank with hair pin shaped tubes secured thereto, those tubes extending within the vat.
In the above known embodiment, a first fluid circulates in the vat, which vat is possibly provided with baffles, while a second fluid circulates in the tubes, which second fluid is brought at one end of the tubes by a first collector box and collected from the second end of the tubes by a second header tank.
The known heat exchangers of the above mentioned type are satisfactory regarding the heat exchange capacity they have. But it may happen that leaks will occur, in particular at the feet of the tubes engaged in the header tanks closing the vat in which circulates the first fluid. Leeks may also be provided through perforations of the thin walled tubes having walls generally of about 6-8 tenths of a millimeter.
Actually, experiments have shown that fluids circulating in heat exchangers can carry waste products, and particularly metal chips. This is for example the case for lubricants of gear mechanisms. It thus happens sometimes that such metal chips will remain at a fixed place in the circuit of the heat exchanger while being submitted to a movement making that these metal chips produce a milling action which may cause a perforation of the wall of the circulation duct.
Present safety requirements in particular in the aeronautical industry, make that some components, such as are the heat exchangers, must be able to work during many hundreds of thousands of hours without any failure occurring because of these heat exchangers.
It has thus been found that the hereabove mentioned problems concerning the safety of use while ensuring a very good effectiveness with respect to the heat exchange lead to avoid to use heat exchangers of the tubular core type.